Watershed Modeling and

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Watershed Modeling and GIS Applications
Jeff Arnold ARS- Temple, Texas
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Possible Configurations
? Subwatersheds ? Hydrologic Response Units ?
Output from other Models - EPIC, SWAT ? Point
Sources - Treatment Plants
Stream Delineation
 
 
 
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Subbasins and Streams
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Subbasins and Streams
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SWAT Watershed System
Channel/Flood Plain Processes
 
 
 
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Hydrologic Balance
Evaporation and Transpiration
Precipitation
Surface Runoff
Root Zone
Infiltration/plant uptake/ Soil moisture
redistribution
Lateral Flow
Vadose (unsaturated) Zone
Revap from shallow aquifer
Percolation to shallow aquifer
Shallow (unconfined) Aquifer
Return Flow
Confining Layer
Flow out of watershed
Deep (confined) Aquifer
Recharge to deep aquifer
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Nitrogen Cycle
Atmospheric N fixation (lightning arc discharge)
Harvest
NH3
Symbiotic fixation
N2 N2O
fertilizer
fertilizer
runoff
manures, wastes and sludge
ammonia volatilization
denitrification
Soil Organic Matter
mineralization
immobilization
NH4
immobilization
NO3-
NO3-
NO2-
ammonium fixation
anaerobic conditions
clay
nitrification
leaching
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Pesticide Dynamics
Foliar Application
Surface Application
Degradation
Runoff
Washoff
Infiltration
Degradation
Leaching
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Water, Nitrogen and Phosphorus Uptake
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Climate Change
Radiation Use Efficiency Adjusted for CO2
ET Penman-Monteith Canopy Resistance
Adjusted for CO2 Impact on Leaf
Conductance
CGM Estimates of Precip, Temperature, Humidity,
Solar Radiation, Wind Speed
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Management
? Crop Rotations ? Removal of Biomass as
Harvest/ Conversion of Biomass to Residue ?
Tillage / Biomixing of Soil ? Fertilizer and
Manure Applications ? Edge-of-Field Buffers ?
Pesticide Applications ? Irrigation ? Water
Impoundment (Wetlands, Rice)
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Channel Processes
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ArcView GIS Interface
Land Use Inputs Type Ag, Forests,
Range, Urban Management Rotations
Tillage, Irrigation, Fertilizer
Topographic Inputs Subbasin Delineation
Routing Structure Channel Slopes Lengths
Overland Slopes Lengths
 
 
 
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Need for Models in the U.S.
? US EPA Watershed Assessments ? NRCS
National Conservation Assessments Climate
Change Water Supply Irrigation Management
 
 
 
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Observed (USGS)
Validation of Flow and Sediment
SWAT Simulated
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HUMUS Scenario Reduction due to 2 million miles
of buffers
Sediment Reduction
Phosphorus Reduction
Nitrogen Reduction
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The National Elevation Dataset
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The Shuttle Radar Topography Mission (SRTM) used
radar instruments to collect data for the most
detailed, near global topographic map of the
Earth ever made

• 1 arc-second elevation data for the United
  States
• 3 arc-second data for the globe

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1-arc second (30 meter) SRTM data postings of the
continental United States can now be obtained in
two ways via the USGS EDC Seamless Distribution
System http//seamless.usgs.gov/

• Electronic Download
• Media (CD)

Updated 21 May 2003 USGS is now distributing
elevation data from SRTM for South America and
North America - 90m resolution
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National Land Cover Dataset
Mid-1990s Landsat Thematic Mapper satellite
data 21-class land cover classification scheme 30
meter spatial resolution
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Daily Precipitation and Temperature
6,000 Stations 30 Years
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NEXRAD Doppler Radar Network
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BLUE River Oklahoma
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Model Validation
Limited Validation at Application Watersheds
Need Research Watersheds for Comprehensive
Validation across Ecosystems Continuous Flow
and Sediment Data 30-60 Yrs
 
 
 
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USGS Water Watch
Web access to USGS water resources data in real
time
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USGS National Water Information System

• Real-time and Historic Data
• Streamflow and stage
• Groundwater levels
• Water Quality
• Site information
• Tabular or Graphical Format

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